There is a strong tendency across the world to amalgamate political jurisdictions, especially local governments. Merger of jurisdictions entails integration of local interests, and former jurisdictions have to struggle to secure political representation and specific area interests in the new amalgamated jurisdiction. We argue that this struggle is affected by the strength of the centre–periphery dimension of the new amalgamated jurisdiction. When a large city is merged with less populated jurisdictions, a strong centre–periphery dimension is created, and this leads to a numerical over-representation of the periphery in the legislature of the amalgamated jurisdiction. We test the argument empirically using a recent large-scale amalgamation reform that allows us to compare 66 amalgamations with different centre–periphery dimensions. Our argument is supported when we examine representation by seats in jurisdiction councils (descriptive representation) and politicians’ advancement of local interests (substantive representation).